/**
 * 动态属性；
 * 采用代理；
 * 可以链式调用；
 */
export const add = new Proxy(
  { _store: 0 },
  {
    get(target, prop, receiver) {
      if (prop === Symbol.toPrimitive) {
        return () => target._store;
      }
      target._store += +(prop as String);
      return receiver;
    },
  }
);

const count = add[2][3][5] + 100;
